The general hypothesis that the foraging behavior and distribution of high level marine predators (sea otters and shorebirds) under natural conditions are mediated by benthic prey toxicity due to harmful algal blooms (HAB's) will be tested in two geographic regions regions (California and Alaska). Because benthic community structure is often controlled from the top down via predation, the influence of phytotoxins in these habitats will be further amplified if key predators avoid entire regions or prey populations regularly exposed to toxic blooms. In southeast Alaska, the general hypothesis that sea otter foraging is regulated by paralytic shellfish poisoning toxins (PSPT) distribution will be tested by determining: 1) whether or not the expanding southeast Alaskan sea otter population has occupied inside passage sites where butter clams are abundant but contain biologically significant levels of PSPT year round, and 2) if so, whether the sea otters have either shifted their diet away from their primary butter clam prey to alternate non toxic species, or are continuing to eat butter clams, but perhaps while discarding the most toxic body parts. The second research component will focus on the response of three common northern California shore birds (Godwits, Dowitchers, Oystercatchers) to the predictable seasonal increase in the PSPT content of two major intertidal invertebrate prey (mole crabs and mussels). The general hypothesis that the foraging strategies of these avian predators is also mediated by PSPT will be tested by monitoring and correlating seasonal changes in invertebrate prey toxicity levels with changes in the foraging behavior and distribution of the birds at several widely separated sites along the California coast.
